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Tree-ring proxies and the divergence problem

What the science says...

Select a level... Basic Intermediate

The divergence problem is a physical phenomenon - tree growth has slowed or declined in the last few decades, mostly in high northern latitudes. The divergence problem is unprecedented, unique to the last few decades, indicating its cause may be anthropogenic. The cause is likely to be a combination of local and global factors such as warming-induced drought and global dimming. Tree-ring proxy reconstructions are reliable before 1960, tracking closely with the instrumental record and other independent proxies.

Climate Myth...

Tree-rings diverge from temperature after 1960

Actual reconstructions "diverge" from the instrumental series in the last part of 20th century. For instance, in the original hockey stick (ending 1980) the last 30-40 years of data points slightly downwards. In order to smooth those time series one needs to "pad" the series beyond the end time, and no matter what method one uses, this leads to a smoothed graph pointing downwards in the end whereas the smoothed instrumental series is pointing upwards — a divergence (Climate Audit).

At a glance

"Trees tell of past climates: but are they speaking less clearly today?" That was the intriguing title of a paper published in the peer-reviewed journal, Philosophical Transactions of the Royal Society of London, in 1998. The authors discussed various aspects of the use of tree-rings as representatives - or proxies - of past climatic patterns.

Tree growth is sensitive to temperature. Because of that, warmer wetter periods produce wider tree-ring patterns. When it's colder and dryer, the rings are narrower, indicating slow growth. In this way, the width and density of tree-rings in ancient trees serve as a proxy for temperature. That makes it possible to reconstruct temperature records going back over many centuries. For example, historic events such as major volcanic explosions tend to lead to global cooling. Such events show up very well in tree-ring reconstructions.

In more recent times, since the late 19th century, we also have the observational temperature record to compare with tree-ring reconstructions. Agreement between the two datasets is at first close. However, in middle and especially high latitude sites, the correlation breaks down after 1960. At this point, while temperatures rise, tree-ring width shows a falling trend - a decline. This divergence between temperature and tree growth is called, imaginatively enough, the divergence problem.

The decline, or divergence problem had been recognised, regularly discussed and written about since around 1995. That's 14 years before anyone had ever heard of 'climategate' and the song and dance that the science–deniers made of 'hide the decline'. If anything should serve as a quality-control alert for the output of science-deniers, it's right there.

Now, everything that happens has a cause, but not all causes are straightforward. There are plenty of ways to put stress on plants and stress makes growth-patterns abnormal. The trouble is that such stress-factors often vary in an irregular fashion and independently of one another. Even in a 2023 paper, the detailed cause of the divergence problem was described as being accompanied by 'significant controversies'. It's real, but it's complicated, in other words.

Temperature-induced drought stress and changes in seasonality are likely to be relevant here. Also likely to have had a role is the phenomenon of ‘Arctic dimming'. The term 'dimming' refers to reduced sunshine reaching the surface in some circumpolar regions, due to industrial aerosol pollution. Northern Hemisphere pollution tends to accumulate over the Arctic. Reduced sunshine affects photosynthesis and in return that impacts upon plant health and growth. Indeed, a 2021 paper ominously commented that the effects of Arctic aerosols on net primary production - growth - were particularly important in light of the current race to exploit natural resources north of the Arctic circle.

The extensive boreal forests of the north play a major role in shaping Earth’s carbon cycle and climate system. In the divergence problem, they have raised a red flag. Something up there is wrong and it should come as no surprise that, once again, our reckless misuse of our planet is high on the list of suspects for that.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

"An anomalous reduction in forest growth indices and temperature sensitivity has been detected in tree-ring width and density records from many circumpolar northern latitude sites since around the middle 20th century". This phenomenon, also known as the “divergence problem”, is expressed as an offset between warmer instrumental temperatures and their underestimation in reconstruction models based on tree rings."

Can you guess when that was written?

It's the first few lines of the abstract of a review paper published in 2008. That's a year and nine months prior to all the manufactured controversy of so-called 'climategate', in which issues with tree-rings were seized upon by the usual suspects. But the issues are relatively recent. Here's an explainer.

Tree growth is sensitive to temperature. As a result, tree-ring width and tree-ring density, both indicators of tree growth, serve as useful proxies for temperature. By measuring tree growth in ancient trees, scientists can reconstruct temperature records going back over 1000 years. Comparisons with direct temperature measurements from 1880 to the present day show, for the earlier half of this period, a high correlation with tree growth. However, in high latitude sites, the correlation broke down after 1960. After this point, while observed temperatures rose decade on decade, tree-ring reconstructions showed a falling trend. This is what is known as the divergence problem.

The divergence problem has been discussed in the peer reviewed literature since the mid 1990s when it was noticed that Alaskan trees were showing a weakened temperature signal in recent decades (Jacoby & D'Arrigo 1995). This work was broadened in 1998 using a network of over 300 tree-ring records across high northern latitudes (Briffa et al. 1998). From 1880 to 1960, there is a high correlation between the instrumental record and tree growth. Over this period, tree-rings are an accurate proxy for climate. However, the correlation dropped off sharply after 1960. At high latitudes, there has been a major, wide-scale change in tree-growth over the past few decades.

Figure 1: Twenty-year smoothed plots of tree-ring width (dashed line) and tree-ring density (thick solid line), averaged across a network of mid-northern latitude boreal forest sites and compared with equivalent-area averages of mean April to September temperature anomalies (thin solid line). Graphic from Briffa et al. 1998.

Has this phenomenon happened before? In other words, can we rely on tree-ring growth as a proxy for temperature? Briffa and colleagues show that tree-ring width and density show close agreement with temperature back to 1880. To examine earlier periods, one study split a network of tree sites into northern and southern groups (Cook et al. 2004). While the northern group showed significant divergence after the 1960s, the southern group was consistent with recent warming trends. This has been a general trend with the divergence problem - trees from high northern latitudes show divergence while low latitude trees show little to no divergence.

The important result from Cook et al was that before the 1960s, the groups tracked each other reasonably well back to the Medieval Warm Period. Thus, the study suggests that the current divergence problem is unique over the past thousand years and is restricted to recent decades.

That this is a relatively recent phenomenon suggests that the decline in tree growth may have at least a partial anthropogenic cause. A thorough review of the many peer reviewed studies investigating possible contributing factors can be found in 'On the ’divergence problem’ in northern forests: A review of the tree-ring evidence and possible causes' (D’Arrigo et al. 2008). Some of the findings of the review were as follows.

Various studies had noted the drop in Alaskan tree-growth coincided with an increase in warming-induced drought. Combined temperature and rainfall records showed that growth declines were more common in the warmer, drier locations. In addition, studies in Japan and Bavaria suggested that increased sulphur dioxide emissions had a role.

Indeed, as the divergence problem is widespread across high northern latitudes, there may be a large-scale explanation, possibly related to airborne pollution effects. A later study (Briffa et al. 2004) proposed that falling stratospheric ozone concentration was a possible cause of the divergence, since this observed ozone decline has been linked to an increased incidence of ultraviolet (UV-B) radiation at the ground.

Another factor at those high latitudes was what is known as global dimming - a drop in solar radiation reaching the ground. The average amount of sunlight reaching the ground declined by around 4 to 6% from 1961 to 1990. That is almost certainly down to aerosol-based industrial pollution.

One study suggested that microsite factors are an influence on whether individual trees are vulnerable to drought stress. Such factors included the slope where the tree is located, the depth to permafrost and other localised factors (Wilmking & Singh 2008). This paper amusingly refers to the divergence problem as the "divergence effect" so as "to not convey any judgement by the wording" (you wouldn't want to offend those overly sensitive Alaskan trees).

In summary, there is evidence for local, regional and global causes all being involved with the divergence problem. It's a complex combination of various contributing and interacting factors, often unique to different regions and even individual trees. At the time of writing, early 2024, it's still being discussed (e.g. Büntgen et al. 2021Cai & Lu 2023; abstract in English). So that's what 'hide the decline' was all about. The divergence problem - a particularly complex issue with multiple interacting causes that affects tree-ring records since 1960. Fortunately, we have been able to directly measure and average out global temperature for over a century now, so we know it's warming anyway. But the divergence problem - the decline - is a fascinating area of research in its own right.

Last updated on 1 May 2024 by John Mason. View Archives

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Comments 26 to 50 out of 89:

  1. Thanks michael Mann responds by deleting problematic sets from his 2008 paper one at a time, not by deleting them all at once. I'd like to know where he deletes both bristlecone and Tiljander sets at the same time. You have a very malleable definition of a hockey stick. No one anymore defends a millenium graph with a straight handle and 20th century blade such as appeared in the IPCC's 2001 report to (-Snip-). Why can't you just admit that Mann and the IPCC got it wrong?

    [DB] perhaps you missed this warning about needed compliance with the Comments Policy.  This site is about the science of climate change, not about scoring rhetorical points.

    Inflammatory rhetoric snipped.

  2. dawsonjg, You obviously have not actually bothered to *read* the Mann 2008 paper or the associated SI (and the online update at Mann's personal website). Mann did a reconstruction, reported in the main paper, which excluded all of the dendro proxies. He got essentially the same answer although it was not statistically significant as far back in time as the full recon. In the SI, he tested the results of leaving out the problematic proxies (Tiljander and a couple of others) to test the sensitivity of the main recon to these proxies. No big differences. As a result of complaints in the blogosphere Mann reported in the updated SI the result of tests which left out the Tiljander data and the dendro data. The result of this was reduced significance in the earliest part of the no dendro/no Tiljander part of the reconstruction, mostly due to the fact that Tiljander represented a significant part of the earliest data. So did Mann 2008 get it wrong? I would say no. He showed that dendro evidence is a valid proxy, in spite of the attacks mounted on it by the denialists. There are almost certainly not enough non dendro proxies with sufficient resolution to do a long recon with nothing but non dendro evidence. The fact that Mann 2008 agrees broadly with other reconstructions despite differences in proxy selection and analytical methodology would seem to indicate that he is in the ballpark. We'll never know with any certainty what the exact history of global temperature is over the last couple of millennia but I think that it is possible to get a pretty good idea of what happened by using the multiproxy methods which Mann pioneered.

    [DB] In addition to your sage advice, and also the reading of the OP and the other comments above, this post at RC by Tamino is relevant:

  3. dawsonjg... "Why can't you just admit that Mann and the IPCC got it wrong? " You're describing science at it's best. Mann's work in 1998-99 was new and different. Why would you expect it to be correct by today's standards? Do we expect Darwin's work to be correct by today's standards? No. But what I would say about Mann's work (as with Darwin) is that it has stood up to intensive, hostile scrutiny and has lead to a better understanding of the subject matter today. What more could you want from science?
  4. dawsonjg... Peter Hadfield (Potholer54) has a youtube video I've always enjoyed titled "The Scientific Method Made Easy." I'm not trying to be patronizing here but there is an element that he brings up in the video that I always find interesting. He says (paraphrasing), "Whether other researchers think John (the "evil" scientist in his example) cheated or just got things wrong doesn't matter because his work won't be consistent with other research and will eventually be discarded." Ultimately what all scientists want is to get things right because that will mean their work will stand the test of time. Even if Mann was (as deniers suggest) trying to push fraudulent work it doesn't matter because if he was it wouldn't fit the broader body of research. What has happened though is Mann's work has fit quite well. Other researchers have been able to reproduce his results with other methods. In fact, there are now almost a dozen multi-proxies that are pretty well consistent with Mann's earlier work. That work has improved on what he did and even Mann's own work has improved on his earlier work. All a case of science doing what it's supposed to do.
  5. Thanks Rob - I know what science is suposed to do. What Mann does is not it at its best. Thanks DB, I've read Tamino's review. I guess comments would be deemed 'beating a dead horse' Thanks jmsuly, I've read some of what you suggested. Might I suggest further reading at ? When you eliminate all the 'problematic' Tiljander and bristlecone data together rather than one at a time, you eliminate Mann 2008's claim to fame. But why their persistent inclusion when it has been acknowledged that they are 'problematic'?
  6. Dawsonjg, Where is your evidence that "When you eliminate all the 'problematic' Tiljander and bristlecone data together rather than one at a time, you eliminate Mann 2008's claim to fame"? here you claim to ask if Mann performed these analysis. here you claim that you have not seen the analysis done. You now claim that the analysis shows Mann was wrong. You are not arguing in good faith.You have been given the information that Mann has done that analysis and it makes no difference in the result, except lowering the statistics. You are now claiming, without any evidence, that Mann is wrong. Please produce some evidence to support your frantic handwaving.
  7. Dawsonjg is referring to this chart reproduced from a chart which I believe to be from the supplementary material of Mann 2009: The original Mann 2008 EIV reconstruction is in red, the no tree ring reconstruction is in blue, the reconstruction with seven series with higher uncertainties (including tiljander) removed is in brown, and the reconstruction with neither tree rings nor the seven series with higher uncertainties is in green. Some things are immediately obvious: 1) The green reconstruction is still a Hockey Stick; 2) The highest temperatures in the MWP in the green reconstruction is still less than current temperatures; 3) The highest temperature in the green reconstruction still lies withing the error bars of the original reconstruction (shaded yellow); and 4) The green reconstruction is still closer to Mann 2008 than to Lamb 1966. These four facts show clearly, according to the deniers, that Mann committed fraud; that Mann's reconstructions of MWP temperatures are entirely in error regardless of how many independent confirmations show the same thing; and that Lamb's 1966 guesstimate was much more accurate than Mann's 2008 reconstruction. More reasonable people might consider these facts to show that Mann's reconstructions are essentially confirmed by this sparse network. They might also conclude that the increased variability is more likely to be due to the restricted number of the remaining data sets rather than because Mann 2008 got anything wrong.
  8. dawsonjg... "Why can't you just admit that Mann and the IPCC got it wrong?" and "Thanks Rob - I know what science is suposed to do" Do you really know - or are you just using the words for rhetorical effect? Why do you fall into the common trap laid by incorrigible denialists of pretending that new science can ever be about presenting 100% perfect papers? That is an impossible standard which has never been achieved or has never been presented (by scientists) as achievable. It is absolutely not how science works. Only the ignorant, or those wishing to twist ordinary people's minds with propaganda, would ever claim that. What you are doing is this. You are misrepresenting the situation by trying to suggest that Mann, by presenting 13 years ago a "first of a kind" paper that was not 100.00% "perfect", was "wrong". Clearly, you do NOT know what science is supposed to do. You, along with all the others like you, are clearly trying a well worn propaganda technique by creating a blizzard of misdirection that because the paper was not 100.00% perfect it must, in the weird, difficult, nit-picky, obstructive way that too many think, be wholly worthless and evidence of incompetence at best and fraud at worst. Deny you are doing that that, dawsonjg. I dare you. The all too familiar use of such innuendo was the reason for my "mole-on-the-face-of-the-supermodel analogy. She remains incredibly beautiful and any minute nit-picky perceived flaws (most of which are misperceived camera artefacts anyway) doesn't in any way take away from that. Similarly, small perceived flaws, even if a few of them are real, in otherwise sound science are only "evidence" that climate science is "wrong" in tinfoil hat land, not in the real world.
  9. This page contains the supplementary material for Mann 2009 (direct link to pdf). The figure provided in post 32 above has been altered from the original (Figure S8, p31). Specifically, the green line before 1500AD is dashed in the original. This is because it does not pass the validation tests. These tests are described in the section titles "Validation Exercises" on p4. To pass the test the reconstruction must rule out a 'red noise' null hypothesis at the 5% significance level. Care should therefore be taken when interpreting the green line. To quote from the "Sensitivity Tests" section, p9: "This additional test reveals that with the resulting extremely sparse proxy network in earlier centuries, a skillful reconstruction is no longer possible prior to AD 1500. Nonetheless, even in this case, the resulting (unskillful) early reconstruction remains almost entirely within the estimated error bounds of the original reconstruction." I think it would have been nice to show uncertainty bands for the green line alone. However, presumably that would require significant CPU time and not add much information.
  10. Michel I have read thoroughly convincing analyses that the hockey stick is 'problematic' (to put it in terms that I hope won't get snipped). But knowledgable people on sites such as this ridicule such analysis as il-motivated nonsense (Mann has been doing this very noisily for nearly a decade, before tacitly backing down very quietly on issue after issue). So who am I to believe? All I can do is read the pro and con arguments and pose a few questions to see if I get credible answers. But accusations that my questions amount to 'frantic handwaving' or 'crafted disinformation' for an industry funded defamation campaign are not very informative. I can't give you evidence re the 2001 graph because that's deemed dead horse territory, I've given some evidence re the 2008 graph above.
  11. @dawsonjg As I understand it; if those "thoroughly convincing analyses that the hockey stick is 'problematic'" have any merit, then they'll be submitted to a credible journal and peer reviewed. If the reviewers feel the 'analyses' have any merit, then they'll be approved for publication and will appear in the next available issue of the journal. Then the scientific community will read and consider the 'analyses', and those with an interest will undertake further work and submit further papers, following the same procedure. That's the scientific process. Whether we like it or not, what is said in blogs is largely irrelevant to the consensus view of the science at any particular moment. What Mann wrote a decade or more ago can really never be 'wrong', as it represented the best understanding of the science at the time it was written. If subsequently someone can show that a paper is flawed in some way, then, more often than not, the original author is likely to write another paper correcting any flaws and incorporating the new ideas. That's how knowledge of climate science develops. It's what Steven Schneider did in the 70's when he realised that the paper he'd written predicting forthcoming cooling was based on an over-simple model, and the fact was we were actually warming. As a layman, I find this quite easy to understand. It's a logical procedure that works well. Don't you think so?
  12. dawsonjg @37, if you cut of the "snake" at 1000 AD (the duration of the MBH 99 hockey stick) then it isn't a snake. Still less so if you cut it of of at 1600 AD to compare it with MBH 98. This ignores the fact that by drastically restricting the data available for the reconstruction, it was inevitable that the green line above should show more variability. The simple fact is that through all your inuendo you have carefully kept the data of stage, and the reason is obvious. When the data is placed front and center your case transparently evaporates, and all you are left doing is playing word games. It should of course be noted that you have not said anything to impugn any of the many other reconstructions which confirm Mann et al 2008's result. Nor, quite frankly have you presented a single substantive reason to think there is anything wrong with any of the proxies used in Mann et al 2008 to begin with. Your entire case todate has consisted of asking some rhetorical questions on another thread, and asserting on this one without evidence that the proxies where "problematic". That apparently is enough to count as evidence in your mind.
  13. You describe the way the review process should work John Russell, the way it worked for Einstein and the way it still works in some fields such as medicine. But consider who controls the billions of dollars poured into climate research and who influences the peer review process and who has been claiming that the debate is over and anyone who disagrees is an industry funded denier - imagine where we would be if Einstein had politicised the process in that way. And investigate what MM had to go through to get their peer reviewed papers published. And consider whether the graphs presented above would ever have replaced the 2001 hockey stick if McIntyre and a few others had not navigated the obstacles and weathered the vilification to prove it was 'problematic'.
    Response: [muoncounter] Accusation of fraud, conspiracy, etc violate the Comments Policy. Einstein did not go through 'peer review.'
  14. dawsonjg, you should learn about how science works--including funding--before making such extreme claims. It is obvious that you never have been a published scientific researcher who has applied for funding, been accepted and rejected for funding, and has reviewed funding proposals. Nor do you understand the difference between funding of research and peer reviewing of research results that were produced regardless of the funding of the work that produced those results. You can start learning with historian Spencer Weart's account of the history of Keeling's climate research funding and of funding for science in general.
  15. Indeed, Tom D, and dawsonjg could further use some reading on Einstein's life and work--the Isaacson bio is readable enough. Good grief. Dawsonjg, you're working backwards. You're starting with models and trying to disprove physics. Read Weart. Understand the development of the science. There is no multi-generational hoax involving tens of thousands of scientists. I know you will say that you're not making this claim, but your rhetoric strongly implies the claim, and all I know about you and your ability to think comes from the words you string together.
  16. dawsonjg You are stuck on this idea that editors and reviewers can somehow be corrupted by those "billions of dollars," whereever they are, to allow a consensus to develop despite all evidence to the contrary. I am a subject editor at a pretty well read journal and I cannot conceive of how such a thing could happen except in the least populated and most arcane corners of science. You have to understand that people editing and reviewing papers are actually, at some level, professional competitors of the people they edit/review. In fact, the editors deliberately pick the reviewers to reflect a range of opinion/expertise. Editing and reviewing activities also occur in the public eye of at least some of your quite critical peers. The appearance of favoritism or collusion (or the opposite) is very much looked down upon, and often stigmatized. If anything, lack of critical insight in the reviewing process will hurt, not help your chances at getting funding because of the infuence on your reputation as a critical thinker. Knowing someone is no guarantee of a friendly review, either. I have often had to reject papers by people who I consider friends of mine. Given all this, it is really hard for someone truly familiar with the process to comprehend your thinking. Perusing the level of critical discourse even in the "leaked" CRU emails confirms how seriously even those with close working ties interrogate each other about methods etc. If I weren't convinced that you simply didn't have the experience to temper your judgement, I might even find it insulting that you would even intimate that somehow it could as thoroughly corrupted as you suggest. Second, If you think climate science has problems due to the amount of money sloshing around, I can think of no worse counter example than medical science, in which the amount of money sloshing around dwarfs that in climate science. Lots of potential conflict of interest there! Still, as you say, they manage a pretty tight ship...although there are several high profile instances of fraud that pop up now and again.
  17. dawsonjg continues his preference for innuendo rather than facts, on this occasion suggesting that there was no proper scientific critique of MBH 98 and 99 prior to McIntyre and McKittrick's interventions. As it happens, following publication and prior to M&M's intervention MBH 98 and 99 where criticized by Jones 1998 (Nature), Huang, Pollock et al 2000 (Nature), Broecker 2001 (Science), and Esper et al 2002 (Science). Mann responded to these criticisms, agreeing with some points and rebutting others. Mann also published a detailed analysis of the virtues of different climate reconstruction methods, developing the RegEM which was later further improved on to become the EIV algorithm. Hans von Storch also published a methodological paper in 2004 performing a detailed analysis of different algorithms for reconstructions. So, before M&M had even appeared on the scene, the scientific community was conducting an extensive debate on methods of reconstruction and Michael Mann had already replaced the MBH algorithm with a superior one two years before M&M decided to criticize the by by then six year out of date method of MBH 99. Clearly dawsonjg's innuendo of scholarly inaction is a complete fiction and without any basis in fact. What is more, it entirely neglects that no substantive criticism in M&M 2003 or 2005 has stood the test of time, and their most fundamental criticism has been shown repeatedly to be itself flawed far beyond any problems found in Mann's earlier algorithm. Given dawsonjg's continued use of innuendo, complete absence of evidence presented in his case, and defamatory comments, perhaps it is time that he be required to fully comply with the comments policy. Muoncounter, it is a minor point but Einstein did go through peer review.
  18. Tom C, Off-topic here, but Kennefick 2005 showed that peer review (as we know it) did not necessarily apply at Annalen der Physik. As usual, the real story is not as clear as wikipedia would have us believe. But an Einstein throwdown in a denier argument is about as valuable as 'Galileo was outvoted.'
  19. dawsonjg @ 35... "I have read thoroughly convincing analyses that the hockey stick is 'problematic'." We all know what you've been reading and many here have read that same work. But you might stop to consider this... Why did someone go to so much trouble to try to undermine one piece of science? Normally, if a piece of research is poorly crafted and the results are suspect the course of action is to reproduce similar research using different methods to show that the results are erroneous. The new research would conflict and probably supersede the previous research. There you go. Problem fixed. MBH99 shown wrong. Move on with the research. So, why haven't McIntyre or Montford done this? Why do they only operate to try to find flaws without producing any actual research of their own? Why don't we have any multi-proxy reconstructions from them showing a different conclusion? They obviously consider themselves qualified. They obviously have the time and backing to perform such research. But they don't. Why? I can tell you for sure that the Idso's (who are well connected with the same folks) have several hundred studies on the MWP that they've collected and posted online. I've poured through them in detail. But they also don't go so far as to try to produce a multi-proxy reconstruction of that data. Why? You should really go and watch that Peter Hadfield video on the scientific process. Here is the link.
  20. Dawsonjg says, talking about science "What Mann does is not it at its best." One has to wonder then what M&M do should be called; whatever that may be, Wegman's work should wear a similar name. This is recommended reading for all those who think that Dawsonjg or M&M have any kind of a valid point. It reviews the errors in M&M methodology (first identified by David Ritson) and dives deep into the computer code used by M&M, where the explanation lies for their findings. It also clearly demonstrates how Wegman did not truly replicate anything. Dawsonjg has rambled about funding and politics. This contains a nice timeline summary of the emergence of M&M, readers can decide how much the whole thing was influenced by politics and money sources. As usual, with often touted "billions in climate research," fake skeptics make heavy use of the method that consist of accusing others of what they themselves do. It ensures that subsequent denunciation of what is really happening loses all impact, with masses thoroughly confused as to what to believe. They then naturally gravitate toward what they are inclined to believe anyway. All factual information becomes moot. Dawsonjg illustrates very well that feeling in the following quote "So who am I to believe?" Surely enough, he mixes that with "All I can do is read the pro and con arguments." Reading the pro and con arguments found in the press and blogs is the last thing one should do when considering a scientific issue. SkS is a better blog only because it has its roots in the science that has been published. Science publications on the matter considered is what should be read, not arguments from blogs or newspapers. Dawsonjg should know that, as he claims also "I know what science is suposed to do." If one knows what sience is supposed to do, then the "arguments" worthy of consideration are the following, listed by Tom Curtis above: Jones 1998 (Nature), Huang, Pollock et al 2000 (Nature), Broecker 2001 (Science), and Esper et al 2002 (Science). There has been more, Moeberg has been mentioned, along with numerous other reconstructions, some excluding tree rings. All the stuff on blogs and opinions pieces in newspapers are nothing but noise, and, to use some exotic statistical terminology created by M&M, it is not "trendless."
  21. Hey, I have an idea. Lets say Mike Mann is a bumbling researcher who makes mistakes and should be cast into the netherhells with others like him (eg Spenser, Christy, Soon, Baulinus, ... Hansen, Einstein etc). Now lets see what a difference to the science that make. Better? Whoops, still have hockey sticks, global warming and anthropogenic causes...
    Response: [muoncounter] Perhaps dawson should review 'Its not about the hockey stick' for some much-needed perspective.
  22. dawsonjg: What Mann does is not [science] at its best. Before this goes any further, let's get one thing clear. You've acknowledged that working with Mann's data is beyond your capabilities. You've also conceded in #35 that you lack the necessary skills to judge which side's arguments are scientifically sound. It logically follows that you lack the knowledge to critique Mann's work. And from there, it follows that you have absolutely no right to accuse him of bad scientific practice, let alone anything worse. That being the case, perhaps you should show a bit of humility and tone down your rhetoric. Take yourself out of the equation for a moment and think about this in abstract terms. Suppose that on the one hand, lots of respected scientists in a variety of countries and fields have used a variety of methods to arrive at results that basically agree with one another. And suppose that on the other hand, a guy who doesn't understand these disciplines or these methods decides that their conclusions are possibly or probably wrong because he saw a website that attacked one of them. Logically speaking, what's more likely: That all these scientists made errors that somehow turned out to agree with each other? That all these scientists put aside their professional rivalries and personal morality in order to falsify mountains of evidence over generations for some unknown purpose? Or that the guy who doesn't understand the science is easy to mislead? On the Internet, there are sites explaining that the AIDS virus doesn't exist, that chemotherapy is deadlier than cancer, that the Holocaust never happened, that vaccines don't work and that evolution is mathematically impossible. The arguments sometimes sound plausible, and the authors are sometimes actual experts in the relevant fields. They usually have no problem citing instances of "official suppression" of their work, not least because their followers usually can't appreciate the distinction between "suppressed" and "thoroughly debunked countless times" or "correctly viewed by experts as the work of a crazy person." And they usually have no problem coming up with plausible motives for conspiracy, because money and power are at stake in just about any field you can name. I'm sure you know all of this as well as I do, and I'm also willing to bet that you side confidently with the scientific consensus on most or all of these "controversies." So why do you feel justified in throwing that perfectly rational approach out the window here? If you really want to get to the bottom of this argument, that's the first question you need to address, I'd say. Challenging Mann's work before you've even begun to understand it -- let alone all the work done subsequently -- is like showing up for the Tour de France on a plastic tricycle and expecting to win.
  23. dawsonjg wrote: But consider who controls the billions of dollars poured into climate research Ah, the old they've-been-corrupted-by-the-money line. Desperate hand waving. Just for once try looking at the development of climate science. The basic physics were sorted by the 60s, 50 years ago, yet it took until the 80s before the world at large took notice and realised that we could face a very risky future. Only then did the "billions" get ploughed in - after it became clear that we needed a helluva lot more research pronto. Yet denialists portray the situation as if the money had been available up front before any conclusions were drawn and they imply or even state that climate scientists decided to make a grab for it by manufacturing fake science. Somebody should sue these nasty minded traducers for libel.
    Response: [Rob P] all caps changed to bold font. No all caps in the future thanks.
  24. If dawson is going to bring up the "corrupted by the money" argument, I'd have to suggest that main stream climate scientists are not real smart on that aspect (no offense). If they want to get on the real gravy train they should publish work vigorously rejecting AGW and land themselves a lucrative FF funded think tank position. The money researchers make doing actual research is a penny ante game. I would suggest that nearly all climate researchers are motivated merely by the desire to learn more and get things right.
  25. Thanks for the interesting advice guys. Philippe says: 'As usual, with often touted "billions in climate research," fake skeptics make heavy use of the method that consist of accusing others of what they themselves do.' Do I take it from that that billions have been funding 'fake skeptics'? I know about the often touted few million from Exon and McIntyre's travelling expenses, but who pays the rest to whom? That FF gravy train sounds interesting Rob, what's that all about? No innuendo, I'd really like to know.

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